• Earthquakes and Structures
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• 제16권4호
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• pp.391-399
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• 2019

Residual deformation of high-speed railway bridge piers is cumulative under repeated earthquakes, and influences the safety and ride comfort of high-speed trains. This paper investigates the effects of the peak ground acceleration, longitudinal reinforcement ratio, and axial compression ratio on the cumulative deformation through finite element analysis. A simply-supported beam bridge pier model is established using nonlinear beam-column elements in OpenSees, and validated against a shaking table test. Repeated earthquakes were input in the model. The results show that the cumulative deformation of the bridge piers under repeated earthquakes increases with the peak ground acceleration and the axial compression ratio, and decreases with the longitudinal reinforcement ratio.

• 한국농공학회논문집
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• 제57권3호
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• pp.55-63
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• 2015

Embankment of agricultural reservoir started by four major rivers project. Most agricultural reservoirs must insure the agricultural water, they need must be ensured stability of embankment. Recently, there is a growing interest in seismic stability of structure by earthquake. Results of evaluation of the structural stability through seismic vibration test and numerical analysis, maximum displacement and the maximum acceleration is a similar trends. Appeared by increasing occurrence of the value of the displacement and acceleration of the structure with the result long period wave type in accordance with the seismic wave in the case of seismic waves, which shows the results of similar tendency as long period wave type consists of waveform seismic acceleration. Model test and numerical analysis results with in order to increase embankment agricultural reservoir, the displacement was found to ensure it is displayed within one percentage structural stability of the embankment.

• 한국지진공학회논문집
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• 제18권5호
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• pp.253-259
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• 2014

Porcelain surge arrestor is very vulnerable to earthquake but there is very few information on its dynamic characteristics which are necessary to the seismic design. Therefore, the dynamic characteristics of the porcelain surge arrestor are evaluated considering the variation of its cable tension and stiffness by shaking table test. The test results show that the first natural frequencies are 5.3 Hz and 5.2 Hz in the horizontal x- and y-axis directions, respectively, and higher than 30 Hz in the vertical z-axis direction, respectively. The installation of cable on the surge arrestor reduces the horizontal natural frequencies due to the constraint effect of the cable but cable tension has no effect on the natural frequency. Also, the natural frequency is proportional to the stiffness of the surge arrestor. This test result will be used for the seismic design and seismic capacity assessment of domestic substations and contribute to the stability of the electric power supply under earthquake event.

• 대한토목학회논문집
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• 제12권4_1호
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• pp.77-85
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• 1992

유사동적실험은 시험체에 대한 물리적인 실험에 이론적인 수치해석방법을 접목시킨 실험기법으로서, 특히 규모가 큰 시험체에 대하여 진동대실험 보다 효율적으로 지진응답실험을 수행할 수 있도록 최근에 개발된 방법이다. 본 연구에서는 유사동적실험 수행과정에서 발생하는 실험오차를 분석하여 실험결과를 보정함으로서, 내진성능실험을 위해서 유사동적실험기법을 광범위하게 적용할 수 있는 가능성을 제시하고자 한다.

• 한국압력기기공학회 논문집
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• 제15권1호
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• pp.53-61
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• 2019

The seismic capacity of electric cabinets in Nuclear Power Plants (NPPs) should be qualified before installation and be maintained during operation. However it can happen that identical devices cannnot be produced for replacement of devices mounted in electric cabinets. In case of when no In-Cabinet Response Spectrum (ICRS) is available for new devices, ICRS can be generated by using Finite Element Analysis (FEA). In this study we investigate structural response and ICRSs of battery charger which is supplied to NPPs. Test results on the battery charger are utilized in this study. The response is measured by accelerometers installed on the housing of the battery charger and local panels in the battery charger. Numerical analysis model is established based on resonant frequency search test results and validated by comparison with 2 types of earthquake testing results. ICRSs produced from the numerical model are compared with measured ICRSs in the seismic tests. Developed analysis model is a simple reduced model and anticipates ICRSs quite well as measured response in the tests overall despite of its structural limitation.

• Structural Engineering and Mechanics
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• 제82권6호
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• pp.735-745
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• 2022

The suspension thyristor valve can generate tremendous vertical acceleration responses in layers and large tension forces in hangers. A shaking table test of a scaled-down model of thyristor valves suspended on a hall building is performed to qualify the risk of vertical uplift of two representative types of valves, the chain valve and the rigid valve. Besides, an analytical model is established to investigate the source of the slackening of hangers. The test results show that the valves frequently experience a large vertical acceleration response. The soft spring joint can significantly reduce acceleration, but is still unable to prevent vertical uplift of the chain valve. The analytical model shows a stiffer roof and inter-story connection both contribute to a higher risk of vertical uplift for a rigid valve. In addition, the planar eccentricity and short hangers, which result in torsional motion of the valve, increase the possibility of vertical uplift for a chain valve. Therefore, spring joints with additional viscous dampers and symmetric layout in each layer are recommended for the rigid and chain valve, respectively, to prevent the uplift of valves.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.188-197
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• 2010

This paper presents experimental results of a series of 1-g shaking table model tests performed on end-bearing single piles and pile groups to investigate the effect of particle size on the dynamic behavior of soil-pile systems. Two soil-pile models consisting of a single-pile and a $4{\times}2$-pile group were tested twice; first using Jumoonjin sand, and second using Australian Fine sand, which has a smaller particle size. In the case of single-pile models, the lateral displacement was almost within 1% of pile diameter which corresponds to the elastic range of the pile. The back-calculated p-y curves show that the subgrade reaction of the Jumoonjin-sand-model ground was larger than that of the Australian Fine-sand-model ground at the same displacement. This phenomenon means that the stress-strain behavior of Jumoonjin sand was initially stiffer than that of Australian Fine sand. This difference was also confirmed by resonant column tests and compression triaxial tests. And the single pile p-y backbone curves of the Australian fine sand were constructed and compared with those of the Jumoonjin sand. As a result, the stiffness of the p-y backbone curves of Jumunjin sand was larger than those of Australian fine sand. Therefore, using the same p-y curves regardless of particle size can lead to inaccurate results when evaluating dynamic behavior of soil-pile system. In the case of the group-pile models, the lateral displacement was much larger than the elastic range of pile movement at the same test conditions in the single-pile models. The back-calculated p-y curves in the case of group pile models were very similar in both sands because the stiffness difference between the Jumoonjin-sand-model ground and the Australian Fine-sand-model ground was not significantly large at a large strain level, where both sands showed non-linear behavior. According to a series of single pile and group pile test results, the evaluation group pile effect using the p-multiplier can lead to inaccurate results on dynamic behavior of soil-pile system.

• 한국산학기술학회논문지
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• 제20권1호
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• pp.217-223
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• 2019

국내외에서 점토층이나 준설토 등이 있는 연약지반을 개량하고, 그 지반위에 구조물을 건설하는 수요는 점차적으로 늘어나고 있다. 그리고 이러한 개발과 더불어 태풍, 산사태, 지진 등과 같은 자연재해의 빈도와 규모도 증가하고 있다. 이러한 자연재해로 인한 피해를 예방하기 위한 방법 중 하나가 지반개량공법이다. 본 연구에서는 쇄석을 띠기초 형식으로 설치하였을 때의 주변지반의 가속도 변화를 1-G 진동대 실험을 이용하여 분석하였다. 점토를 이용하여 지반을 조성하고 기초는 쇄석을 띠형식으로 설치하였다. 주기가 다른 입력지진파에 대해 응답가속도와 응답스펙트럼을 분석하였다. 쇄석 띠기초와의 인접거리에 따른 가속도 변화를 분석하여 지진시 쇄석 띠기초가 주변지반의 가속도 변화에 미치는 영향을 평가하였다. Hachinohe 지진파 결과에서는 쇄석띠기초와의 거리에 비해 가속도가 큰 감소는 없지만, 두가지 지진파에 대한 최대응답가속도가 쇄석띠기초와의 거리에 반비례하였다. 응답스펙트럼 분석결과, 장주기와 단주기 입력파에서의 감쇠되는 주기가 달랐으며, 이와 같은 응답스펙트럼 변화가 가속도의 최대가속도값에 영향을 준 것으로 판단된다. Hachinohe 지진파에서는 쇄석띠기초와 멀어질수록 0.08~0.5초 사이의 주기에서 감쇠가 컸으며, Northridge 입력파에서는 쇄석띠기초와 멀어질수록 0.2초 이내의 주기에서 감쇠가 컸다.

• 한국지반공학회논문집
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• 제25권11호
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• pp.27-38
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• 2009

본 연구에서는 조밀한 포화 사질토 지반과 느슨한 포화 사질토 지반에 근입된 모형말뚝을 대상으로 다양한 말뚝휨 강성과 입력 가속도 진폭, 그리고 입력 가속도 진동수 조건에서 1g 진동대 실험을 수행하였다. 그 결과로, 조밀한 포화 사질토 지반조건에 대해, 각 실험 p-y 곡선 상 최대 지반 반력이 나타나는 꼭지점들을 연결하여 등가정적해석에 적용할 수 있는 동적 p-y 중추곡선을 쌍곡선 함수로 나타내었으며, 중추곡선을 쌍곡선 함수로 나타내는데 필요한 초기 기울기($k_{ini}$)와 극한 저항력($p_u$)을 결정하기 위한 경험식을 마찰각과 구속압의 함수로 제안하였다. 제안한 동적 p-y 중추곡선의 적용성을 기존 문헌에 발표된 원심모형실험 결과와 비교하여 검증하였으며, 실제 설계에 적용되고 있는 기존의 p-y 곡선들과도 비교, 분석하였다. 또한 느슨한 포화 사질토 지반조건에서, 진동 중 발생하는 과잉간극수압에 따라 지반 저항이 감소하는 정도를 나타내는 동적 지반 저항 감소 계수($S_F$)를 제안하였다.

• Earthquakes and Structures
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• 제4권1호
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• pp.63-84
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• 2013

A semi-active mass damping (SMD) system with magnetorheological (MR) dampers focusing on low- and mid-rise buildings is proposed in this paper. The main purpose of this study is to integrate the reliable characteristics of the traditional tuned mass damper (TMD) and the superior performance of the active mass damper (AMD) to the new system. In addition, the commonly seen solution of deploying dense seismic dampers throughout the structure nowadays to protect the main structure is also expected to switch to the developed SMD system on the roof with a similar reduction performance. In order to demonstrate this concept, a full-size three-story steel building representing a typical mid-rise building was used as the benchmark structure to verify its performance in real life. A numerical model with the interpolation technique integrated was first established to accurately predict the behavior of the MR dampers. The success of the method was proven through a performance test of the designated MR damper used in this research. With the support of the MR damper model, a specific control algorithm using a continuous-optimal control concept was then developed to protect the main structure while the response of the semi-active mass damper is discarded. The theoretical analysis and the experimental verification from a shaking table test both demonstrated the superior mitigation ability of the method. The proposed SMD system has been demonstrated to be readily implemented in practice.